The primary goal of this project is to contribute to the modeling of the processes involved in auditory comprehension, through a better understanding of the deficit in auditory comprehension that has been associated with "agrammatic" aphasia. Proposed manipulations are intended to more sharply define the impaired components of auditory comprehension, to investigate dissociations and associations in comprehension abilities and to determine whether any of the dissociations now demonstrated in the productive abilities of "agrammatic" aphasics are mirrored in components of comprehension. Specifically, the possibility that difficulty processing the negative morpheme in "pure definitional negatives" may be associated with difficulty processing other semantic phenomena will be investigated to determine if there are theoretically interesting sets of semantically defined functions that are at risk in aphasia. Furthermore, if these problems are related to a change in semantic access procedures, it may be possible to observe consistent relations between them and the failure to show normal priming in lexical decision tasks. This project also begins to examine the auditory comprehension of a variety of sentence types associated with so-called "agrammatic" aphasia across a broad spectrum of patients to determine 1) whether the same dysfunction uniformly effects all implicated sentence types and 2) whether the difficulty is specific to any particular aphasic sub-group. Finally, this project initiates a study of the recovery of auditory comprehension beyond the period usually associated with spontaneous recovery. Observed improvements in patients at a point more than two years post-stroke suggest more systematic observation of progress would be useful. In pursuing these goals, a battery of clinical and experimental tests will be developed to allow adequate description of patients both to observe progress and to select patients for appropriate experimental studies. Proposed work will include both group studies and case studies as dictated by the hypotheses under consideration and the profiles of the patients available.